Positive electrode for lithium-sulfur battery and lithium-sulfur battery comprising same

Abstract

The present disclosure relates to a positive electrode for a lithium-sulfur battery, comprising a sulfur-carbon composite having a plurality of island-shaped carbon coating layers on its surface, and a lithium-sulfur battery including the same. The positive electrode for a lithium-sulfur battery according to the present disclosure has an excellent electrochemical reactivity, which allows the lithium-sulfur battery including the same to have high capacity, high output and long cycle life.

1 . A positive electrode for a lithium-sulfur battery, comprising:
 a positive electrode current collector; and   a positive electrode active material layer positioned on at least one surface of the positive electrode current collector,   wherein the positive electrode active material layer comprises a sulfur-carbon composite having a plurality of island-shaped carbon coating layers on its surface as a positive electrode active material.   
     
     
         2 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein each of the plurality of island-shaped carbon coating layers comprises reduced graphene oxide. 
     
     
         3 . The positive electrode for a lithium-sulfur battery according to  claim 2 , wherein the reduced graphene oxide has a specific surface area of 700 m 2 /g or more. 
     
     
         4 . The positive electrode for a lithium-sulfur battery according to  claim 3 , wherein the reduced graphene oxide has a specific surface area of 700 to 1500 m 2 /g. 
     
     
         5 . The positive electrode for a lithium-sulfur battery according to  claim 2 , wherein the reduced graphene oxide is included in an amount of 0.5 to 3% by weight, based on the total weight of the positive electrode active material. 
     
     
         6 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein the positive electrode active material has a specific surface area of 20 to 50 m 2 /g. 
     
     
         7 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein the positive electrode active material has a pore volume of 0.3 to 0.5 cm 3 /g. 
     
     
         8 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein a pore size in the positive electrode active material is 30 to 70 nm. 
     
     
         9 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein a ratio of a specific surface area of the positive electrode active material relative to a specific surface area of a sulfur-carbon composite that does not include a carbon coating layer is 1 to 3. 
     
     
         10 . The positive electrode for a lithium-sulfur battery according to  claim 1 , wherein the positive electrode active material layer further comprises a carbon bridge connecting the positive electrode active materials. 
     
     
         11 . The positive electrode for a lithium-sulfur battery according to  claim 10 , wherein the carbon bridge basis a crumpled structure or has a fibrous shape. 
     
     
         12 . A method for preparing a positive electrode for a lithium-sulfur battery, comprising steps of:
 preparing a reduced graphene oxide dispersion by dispersing reduced graphene oxide into a dispersion medium;   preparing a sulfur-carbon composite having a plurality of island-shaped carbon coating layers on its surface by mixing the reduced graphene oxide dispersion and a sulfur-carbon composite and drying a mixture;   preparing a positive electrode slurry composition including the sulfur-carbon composite having the plurality of island-shaped carbon coating layers; and   applying the positive electrode slurry composition on at least one surface of a positive electrode current collector to obtain the positive electrode of  claim 1 .   
     
     
         13 . The method for preparing a positive electrode for a lithium-sulfur battery according to  claim 12 , wherein the dispersion medium comprises a lower alcohol. 
     
     
         14 . A method for preparing a positive electrode for a lithium-sulfur battery, comprising steps of:
 preparing a pre-dispersion including reduced graphene oxide;   preparing a positive electrode slurry composition by adding the pre-dispersion to a mixture including a sulfur-carbon composite and a binder; and   applying the positive electrode slurry composition on at least one surface of a positive electrode current collector to obtain the positive electrode of  claim 1 .   
     
     
         15 . A lithium-sulfur battery comprising:
 the positive electrode for a lithium-sulfur battery according to  claim 1 ;   a negative electrode; and   an electrolyte.